Mycobacterium avium subspecies paratuberculosis (MPT) is the causative agent of Johne's disease (JD), which causes chronic granulomatous enteritis in ruminants. Clinically affected animals develop chronic diarrhea and progressive weight loss that eventually results in death, while subclinically infected animals mainly have decreased production of milk. JD is of tremendous economic importance to the worldwide dairy industry, causing major losses due to reduced production and early culling of animals with estimates of 20% of U.S. dairy herds affected and costs of $220 million per year to the dairy industry (Wells, et al. 2000. J. Am. Vet. Med. Assoc. 216:1450-1457). Cattle are most susceptible to infection with this organism within the first 6 months of life, but disease typically does not become evident until 3 to 5 years of age. Infection occurs by ingestion of contaminated manure, colostrum, or milk from infected cows (Sweeney, 1996. Vet. Clin. N. Am. Food Anim. Pract. 12:305-312). Fetal infection also occurs, particularly in pregnant cows with advanced disease (Sweeney, et al. 1992. Am. J. Vet. Res. 53:477-80). Although JD is an important infectious disease of ruminants, there is no effective vaccine against this disease. The only currently available vaccine in the United States consists of killed M. avium subsp. paratuberculosis in an oil adjuvant (Kormendy, B. 1992. Acta Vet. Hung. 40:171-184; Larsen, et l., 1978. Am. J. Vet. Res. 39:65-69). However, such vaccination programs have raised serious public health concerns. For example, at least one veterinarian was accidentally inoculated in the hand during vaccination of animals (Patterson, et al., (1988) J. Am. Vet. Med. Assoc. 192:1197-1199). Further, studies have demonstrated that there is a strong reaction at the injection sites after vaccination with this killed bacteria (Kormendy, B. 1992. Acta Vet. Hung. 40:171-184; Larsen, et l., 1978. Am. J. Vet. Res. 39:65-69). Another drawback of this vaccine is that the vaccinated animals become tuberculin skin test positive (Kormendy, B. 1992. Acta Vet. Hung. 40:171-184; Larsen, et l., 1978. Am. J. Vet. Res. 39:65-69). Thus, there is a need for the development of more effective vaccines against JD that can be used as safe and effective prophylactic and/or therapeutic compositions for MPT infection.